[cfi] Support sanstats if binary is not available in the original location

[vitalybuka]

Summary

By default sanstats search binaries at the same location where the were when
stats was collected. Sometime you can print report immediately or need to move
post-processing to another workstation. To support this use-case if original binary is missing sanstats will fall-back to directory with sanstats file.

[vitalybuka]

ping

[pcc]

Test case?

[vitalybuka]

test

[vitalybuka]

done

[vitalybuka]

ping

[pcc]

LGTM

llvm/tools/sanstats/sanstats.cpp

 // This tool dumps statistics information from files in the format produced
 // by clang's -fsanitize-stats feature.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/Symbolize/Symbolize.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
 #include "llvm/Transforms/Utils/SanitizerStats.h"
 #include <stdint.h>
 
 using namespace llvm;
 
 static cl::opt<std::string> ClInputFile(cl::Positional, cl::Required,
                                         cl::desc("<filename>"));
 

 }
 
 const char *ReadModule(char SizeofPtr, const char *Begin, const char *End) {
   const char *FilenameBegin = Begin;
   while (Begin != End && *Begin)
     ++Begin;
   if (Begin == End)
     return nullptr;
-  StringRef Filename(FilenameBegin, Begin - FilenameBegin);
+  std::string Filename(FilenameBegin, Begin - FilenameBegin);
+
+  if (!llvm::sys::fs::exists(Filename))
+    Filename = std::string(llvm::sys::path::parent_path(ClInputFile)) +
+               std::string(llvm::sys::path::filename(Filename));
 
   ++Begin;
   if (Begin == End)
     return nullptr;
 
   symbolize::LLVMSymbolizer::Options SymbolizerOptions;
   SymbolizerOptions.Demangle = ClDemangle;
   SymbolizerOptions.UseSymbolTable = true;